The current development towards truly mobile computing and networking has brought on the evolvement of various access technologies that also provide the users with access to the Internet when they are outside their own home network. At present, wireless Internet access is typically based on either short-range wireless systems or mobile networks, or both.
Short-range wireless systems have a typical range of one hundred meters or less. They often combine with systems wired to the Internet to provide communication over long distances. The category of short-range wireless systems includes wireless personal area networks (WPANs) and wireless local area networks (WLANs). They have the common feature of operating in unlicensed portions of the radio spectrum, usually either in the 2.4 GHz Industrial, Scientific, and Medical (ISM) band or in the 5 GHz unlicensed band.
Wireless personal area networks use low cost, low power wireless devices that have a typical range of about ten meters. The best-known example of wireless personal area network technology is Bluetooth, which uses the 2.4 GHz ISM band. It provides a peak air link speed of one Mbps, and power consumption low enough for use in personal, portable electronics such as PDAs and mobile phones. Wireless local area networks generally operate at higher peak speeds of 10 to 100 Mbps and have a longer range, which requires higher transmission power, which in turn results in greater power consumption.
Wireless LAN systems are typically extensions of a wired network, providing mobile users with wireless access to the wired network. Examples of wireless local area network technology include the IEEE 802.11a, which is designed for the 5 GHz unlicensed band, and uses orthogonal frequency division multiplexing (OFDM) to deliver up to 54 Mbps data rates; the 802.11b, which is designed for the 2.4 GHz ISM band and uses direct sequence spread spectrum (DSSS) to deliver up to 11 Mbps data rates; and the HIPERLAN Standard, which is designed to operate in the 5 GHz unlicensed band.
In wireless LAN technology, two basic network topologies are available for network configuration: an ad-hoc network and an infrastructure network. An ad-hoc network is formed by two or more wireless terminals without the services of a base station, i.e. in an ad-hoc network the terminals communicate on a peer-to-peer basis. An ad-hoc network is normally formed for temporary purposes. The infrastructure network, in turn, comprises one or more wireless base stations, called access points, which form part of the wired infrastructure. In a typical network of this type, all traffic goes through the access points, regardless of whether the traffic is between two terminals or a terminal and the wired network, i.e. the wireless terminals do not communicate on a peer-to-peer basis. The wireless terminals are typically provided with wireless LAN cards, whereby they can access the wired network or set up an ad-hoc network.
One drawback related to WLAN networks is the limited ability of a wireless terminal to communicate with external wireless communication devices when operating in an infrastructure network. Here, the term “external” is used to indicate that the relevant device is not associated with an access point of the infrastructure network and is therefore not operating in the infrastructure network. The limited ability to communicate with external wireless communication devices in turn translates to an inflexible communication environment. For example, to establish communications between a wireless terminal, such as a laptop, associated with the infrastructure network and a mobile phone not operating in the infrastructure network, it is first required that the mobile phone accesses the infrastructure network. After this, the traffic between the wireless terminal and the mobile phone travels typically through the relevant access point, even though the wireless terminal and the mobile phone are typically in close proximity to each other.
Another alternative for establishing short-distance communications is that the wireless terminal and the mobile phone establish an ad-hoc network for their mutual communications. However, if the wireless terminal enters the ad-hoc operation mode, the existing association in the infrastructure network is normally removed. In other words, the user of the terminal has to be authenticated again and a new association has to be created when the wireless terminal leaves the ad-hoc mode and re-enters the infrastructure network.
Another problem of the WLAN networks involves power consumption, i.e. the battery capacity of the wireless terminals. So far, wireless LAN technology has been used mainly in laptop computers, which are typically AC powered, but which may also be used in battery mode that provides a fairly high battery capacity. To prolong the life of the batteries, the WLAN standards define a specific power save mode into which the terminals may enter from an active mode in order to decrease their power consumption. In this mode, the terminals have to wake up periodically to receive regular beacon transmissions broadcast in the network to enable the terminals to communicate in an orderly fashion. The beacon transmissions indicate, for example, whether there are incoming packets buffered for a terminal. If so, the terminal retrieves the packets, goes back to sleep, and wakes up again to listen to the beacon transmission as per the sleep interval agreement.
The current WLAN power management has been designed assuming that the terminal devices are laptop type computers featuring a relatively high battery capacity. Along with the generalization of various other types of personal communication devices, such as intelligent phones, having a smaller size and thus also a lower battery capacity than laptop computers, power consumption has, however, become a critical issue when new properties are designed for wireless systems and terminals. The above-mentioned inflexibility of the network with regard to the establishment of short-distance communications further aggravates the problem of power consumption, since a link between the external communication device and the relevant access point located further away is needed if an ad-hoc network is not established for a short-distance point-to-point link.
The present invention seeks to accomplish a solution by means of which the flexibility of the WLAN environment may be improved in a manner that enables flexible establishment of low power connections between a wireless communication terminal belonging to a short-range wireless network and an external wireless communication device not belonging to the said network.